That means some digital frames can now “play music and video, in some cases, as well as show multiple pictures on the screen at the same time,” he said.

Last year at this time, there were only 13 digital frames on the market compared to the 70 this Mother's Day, according to a new NPD Group report.

"Digital picture frames grossed nearly $12 million for the week ending May 12, selling more than 112,000 units," the report says.

That means Mother's Day sales were "just as strong in units as frame sales during the week before Christmas," and beat the revenue brought in by digital picture frame sales during the week of "Black Friday," the day after Thanksgiving, according to the report.

However, the frames’ ease-of-use factor and the quality of the photos displayed still leaves a lot to be desired.

At Target’s Web site, for example, some consumers who bought the TruTech 7-inch frame for $89.99 through the retailer have complained about its quality.

“The picture looks like the old TV set I had in college after it gave out 25 years later: Dark, blurry and burned out,” wrote one.

The TruTech frame isn’t the only one to disappoint. Message boards are filled with frustrations about various frames from different manufacturers.

Here are some points to keep in mind if you’re considering buying a digital photo frame:

Bring your card (not just your credit card) to the store: Retailers like Best Buy or Circuit City now carry several photo frames, which they have plugged in and lined up on display.

Take your camera’s memory card, with photos on it, to test out various frames so that you can compare how the photos look for a truer idea of what you’ll be getting.

Make sure the frame you want works with the type of memory card you have, i.e., Secure Digital, Memory Stick and Compact Flash.

Size (resolution and screen) matters: All photo frames — which are basically small LCD screens — are not created equal.

Check to see what the screen’s display resolution is. Rubin of NPD Group recommends a minimum 800x600 resolution.

If that information isn’t on the box, ask the sales person to find out, or check the manufacturer’s Web site.

Most frames come with 5.6-, 7-, 8-, 10- and 15-inch-size screens. The smaller the screen, the smaller those photos are going to look to you.

A 7-inch (diagonal) screen means the photo will be displayed at about 3-1/2-by-5-inch size.

That doesn’t really offer a lot of satisfaction for viewing more than a foot away, especially if the photos being displayed show several people in each picture.

One remote you’ll want nearby: If you think it’s hard to hit the right buttons on your cell phone, you’ll definitely be unhappy trying to maneuver around the back or side of the frame to turn it on or to set other functions.

Choose a frame that comes with a remote control. Not all of digital photo frames do,

Good instructions, software and support: Unfortunately, most digital frames are still not as easy to use as, well, a regular frame.

With a digital frame, you’re going to have to do a little start-up work to get things going. And the quality of the instructions and documentation that comes with the frame make a big difference in the kind of experience you’re going to have, as does the software that is programmed into the frame.

Check the instructions to see if a support phone number or e-mail is listed. If there isn’t any, that’s not a good sign.

The options: Interchangeable frames, USB and batteries: Standard colors for the frame themselves are white, black and various wood shades. Some come with additional frames you can swap out. Sometimes the cost is built-in to the frame purchase; sometimes it’s extra.

For example, one of Philips’ 7-inch Photo Frame includes interchangeable white, red and black frames, and retails for between $160 and $200.

Polaroid sells an $88, 7-inch black frame that you can buy additional frames for at about $8 a pop.

If you don’t want to fuss with a memory card, and want to directly load photos from your computer to the digital photo frame, make sure the frame comes with a USB connector. Some frames also have wireless options.

Also, some, but not all frames come with rechargeable batteries. Without them, you’re tied to a plug in the wall, which limits where you can place the frame.